The Interior Ministry said in a statement that 67 people who were detained after deadly clashes were released Sunday. It was not immediately clear whether others were still being held.

More than 40 people died in the clashes on Friday, some from gunshot wounds, but most in a fire that tore through a trade union building.

Ukrainian Prime Minister Arseniy Yatsenyuk visited Odessa to try to defuse mounting tensions. He said police are being investigated for their failure to maintain order and hinted strongly that he sees Moscow's hand in the unrest.